Light spectroscopic methods, surface analysis

The whole field received a new impetus after the first oil crisis, when Fujishima and Honda reported on the photoelectrolysis of water at Ti02-electrodes [13], Whereas, before the oil crisis, most basic models and results had been published only by 3-4 research groups in the world, many other scientists entered the field after this crisis and studied solar applications, and hundreds of papers were published. Since then, many processes at semiconductor electrodes have been studied more quantitatively by using not only standard electrochemical methods, but also new techniques, such as spectroscopic surface analysis (see e.g. [12]). Naturally, photoeffects played a dominant role in these investigations. These were not only restricted to reactions induced by light excitation within the semiconductor electrode [11], but were also extended to the excitation of adsorbed dye molecules [14,15]. 

At least two Raman spectroscopic methods are applicable in membrane surface characterization Fourier transform Raman spectroscopy (FT-Raman), and micro-Raman spectroscopy (Boccaccio et al., 2002 Gmger et al., 2001 Khulbe and Matsuura, 2000). In FT-Raman the sample molecules are excited with a near-infi ared (NIR) laser and appropriately configured Michelson interferometers, and Fomier transform processes are used in the collecting of scattered light and the analysis of the collected light. Almost the only requirement is that the sample to be analyzed with FT-Raman must not be black (Hendra, 2005). FT-Raman is a valuable tool in determining the overall chemical stmcture of a membrane, but it cannot characterize the asymmetric stmcture of a porous membrane matrix (Boccaccio et al., 2002). 

Close interaction between colloid science and other related disciplines helped in the establishment and further enrichment of its experimental basis. Along with classical experimental methods specific to colloid science (determination of the surface tension, ultramicroscopy, dialysis and ultrafiltration, dispersion analysis and porosimetry, surface forces and measurements of particle interactions, studies of the scattering of light, etc.), such methods as various spectroscopic techniques (NMR, ESR, UF and IR... 

In this chapter we describe advances in the femtosecond time-resolved multiphoton photoemission spectroscopy (TR-MPP) as a method for probing electronic structure and ultrafast interfacial charge transfer dynamics of adsorbate-covered solid surfaces. The focus is on surface science-based approaches that combine ultrafast optical pump probe excitation to induce nonlinear multi-photon photoemission (MPP) from clean or adsorbate covered single crystal surfaces. The photoemitted electrons transmit spectroscopic and dynamical information, which is captured by their energy analysis in real or reciprocal space. We examine how photoelectron spectroscopy and microscopy yield information on the unoccupied molecular structure, electron transfer and relaxation processes, light induced chemical and physical transformations and the evolution of coherent single particle and collective excitations at solid surfaces. 

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